Abstract
PurposeThe purpose of this paper is to study the magnetic properties of the materials Ni1−xCoxMnGe systems by: mean field theory, probability law and high‐temperature series expansions (HTSE) in the range 0≤x≤1. The nearest neighbour J1(x) and the next‐nearest neighbour super‐exchange interaction J2(x) are calculated, using the mean field theory and in the range 0≤x≤1.Design/methodology/approachThe magnetic phase diagrams (TC versus dilution x) and the critical exponents associated with the magnetic susceptibility (γ) and with the correlation lengths (ν) are deduced for Ni1−xCoxMnGe in the ordered phase by HTSE method has combined with the Padé approximants method for the Ni1−xCoxMnGe.FindingsThe obtained magnetic phase diagram of Ni1−xCoxMnGe systems is comparable with those obtained by experiment. The values of critical exponents are nearest to those of 3D Heisenberg model and insensitive to the dilution.Originality/valueBesides the magnetic shape memory effect, the magnetocaloric effect, which exhibits in Ni‐Mn‐Ge or Co‐Mn‐Ge alloys, is of technological interest.
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